I tend to be all elbows when I knit. I need a certain amount of space to feel comfortable, and if you're sitting too close, you're probably going to get prodded with the blunt end of a knitting needle.
I think people who regularly catch my bus in the mornings are learning this. And no one likes to be poked with a knitting needle or have strands of yarn piling up on top of them at 7.15am. Most mornings, no one sits next to me. But it seems that the mornings that I'm concentrating on tricky increases or counting stitches, someone feels that it would just be easier to sit next to me, rather than walk to the empty row two seats back. Why?